Green fish skin collagen extraction method based on fermentation and impurity removal

The invention discloses a green fish skin collagen extraction method based on fermentation and impurity removal, which comprises the following main steps: (1) carrying out liquid culture on bacillus velezensis HL-5, centrifugally collecting thalli, and suspending by using sterile water to prepare a bacillus velezensis liquid seed; (2) cutting the fish skin into pieces, soaking the fish skin pieces with 75% ethanol, draining the fish skin pieces, adding the fish skin pieces into a fermentation tank filled with sterile water, and inoculating bacillus bethecae liquid seeds; (3) the fermentation temperature is 15-20 DEG C, the introduction amount of sterile air is 0.5-2.5 vvm, the rotating speed of the fermentation tank is 150-350 rpm, and the fermentation time is 8-16 h; (4) after fermentation is finished, filtering to remove fermentation liquor, and cleaning and draining the fish skin; and (5) extracting collagen from the fermented and pretreated fish skin by adopting an acetic acid solution or a 0.5 mol/L acet